JP5331051B2 - Light emitting element - Google Patents

Light emitting element Download PDF

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JP5331051B2
JP5331051B2 JP2010097585A JP2010097585A JP5331051B2 JP 5331051 B2 JP5331051 B2 JP 5331051B2 JP 2010097585 A JP2010097585 A JP 2010097585A JP 2010097585 A JP2010097585 A JP 2010097585A JP 5331051 B2 JP5331051 B2 JP 5331051B2
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light
wavelength
light emitting
periodic structure
optical waveguide
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賢児 折田
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Panasonic Corp
Panasonic Holdings Corp
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Matsushita Electric Industrial Co Ltd
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Priority to PCT/JP2010/005415 priority patent/WO2011132239A1/en
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    • H01L33/48Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
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    • G02FOPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
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    • G02FOPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
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    • G02F1/13Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
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    • G02F1/1335Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/1336Illuminating devices
    • G02F1/133615Edge-illuminating devices, i.e. illuminating from the side
    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
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    • G02F1/13Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
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    • G02F1/1335Structural association of cells with optical devices, e.g. polarisers or reflectors
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    • HELECTRICITY
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    • H01L33/00Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/44Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the coatings, e.g. passivation layer or anti-reflective coating
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    • G02F1/00Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
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    • G02F1/00Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
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Description

本発明は、発光素子に関し、特にバックライト光源装置等に用いる発光素子に関する。   The present invention relates to a light emitting element, and more particularly to a light emitting element used in a backlight light source device and the like.

近年、薄型テレビ等の表示装置として、液晶パネルを用いた液晶表示装置の市場が急速に伸びてきている。液晶表示装置は、透過型の光変調素子として液晶パネルと、その裏面に設けられ液晶パネルに光を照射する光源装置とを備えている。液晶パネルは光源装置から照射された光の透過率を制御することにより画像を形成する。光源装置の光源として冷陰極管(CCFL)が用いられてきたが、近年、省エネルギー化の流れによりLED(Light Emitting Diode)素子を用いたLED光源装置の開発が進んでいる。光源としてLEDを用いたLED光源装置は主に2種類に分類することができる。1つ目は、表示画面の真後ろに2次元状にLED素子を配列する直下型であり、2つ目はLED素子を液晶パネルのサイドに配置し、導光板を使用して液晶パネルの背面から光を照射するエッジライト型である。現在、LED光源装置は直下型が主流であるが、液晶表示装置の薄型化の要望に伴い、エッジライト型の開発が進んでいる。   In recent years, the market of liquid crystal display devices using liquid crystal panels as display devices such as flat-screen televisions has been rapidly growing. The liquid crystal display device includes a liquid crystal panel as a transmissive light modulation element, and a light source device that is provided on the back surface of the liquid crystal panel and emits light to the liquid crystal panel. The liquid crystal panel forms an image by controlling the transmittance of light emitted from the light source device. While cold cathode fluorescent lamps (CCFLs) have been used as light sources for light source devices, in recent years, LED light source devices using LED (Light Emitting Diode) elements have been developed due to the trend of energy saving. LED light source devices using LEDs as light sources can be mainly classified into two types. The first is a direct type in which LED elements are arranged two-dimensionally directly behind the display screen, and the second is the arrangement of the LED elements on the side of the liquid crystal panel and using the light guide plate from the back of the liquid crystal panel. This is an edge light type that emits light. At present, the LED light source device is mainly the direct type, but the development of the edge light type is progressing with the demand for thinning of the liquid crystal display device.

従来の液晶表示用のLED素子は、中心波長が約440nmの青色光を発光するLEDチップを覆うように中心波長が約570nmの黄色の蛍光体を塗布した構成である。LEDチップを駆動して青色光を放射させ、放射された青色光を蛍光体に吸収させて黄色光を放射させる。青色と黄色とは補色の関係にあるため、白色光源として機能するLED素子を実現できる。   A conventional LED element for liquid crystal display has a configuration in which a yellow phosphor having a center wavelength of about 570 nm is coated so as to cover an LED chip that emits blue light having a center wavelength of about 440 nm. The LED chip is driven to emit blue light, and the emitted blue light is absorbed by the phosphor to emit yellow light. Since blue and yellow are complementary colors, an LED element that functions as a white light source can be realized.

特開2009−158274号公報JP 2009-158274 A

しかしながら、従来のLED素子をエッジライト型の液晶表示装置のLED光源装置として用いると、LED素子の発光光を効率良く導光板へ入射させることができず、LED素子の発光光の利用効率が悪いという問題がある。導光板への入射光率を向上させるために、LED素子の表面をシリンドリカルレンズである散乱レンズで覆う方法が開示されている(例えば、特許文献1を参照。)。しかし、この場合には導光板の厚さを薄くできないという問題が生じる。LED素子の表面から出射される光の放射角度はいわゆるランバーシャンであり、半値全幅で120°の拡がりを有する光が出射される。このような放射特性を有する発光光の光をレンズにより効率良く集光するためには、レンズの大きさをLED素子の5〜10倍の大きさにする必要がある。LED素子の大きさは約0.5mm×0.5mm程度であるため、レンズの大きさは2.5mm〜5mm程度とする必要がある。一方、効率良く光を導光板に導くためには導光板の厚さをレンズの大きさ程度まで厚くする必要がある。従って、導光板の厚さを2.5mm〜5mm程度とする必要があり、液晶パネルの厚さを薄くするための制限となってしまう。   However, when the conventional LED element is used as an LED light source device of an edge light type liquid crystal display device, the light emitted from the LED element cannot be efficiently incident on the light guide plate, and the use efficiency of the light emitted from the LED element is poor. There is a problem. In order to improve the incident light rate to the light guide plate, a method of covering the surface of the LED element with a scattering lens that is a cylindrical lens is disclosed (for example, refer to Patent Document 1). However, in this case, there arises a problem that the thickness of the light guide plate cannot be reduced. The emission angle of light emitted from the surface of the LED element is a so-called Lambertian, and light having a full width at half maximum of 120 ° is emitted. In order to efficiently collect the emitted light having such radiation characteristics by the lens, the size of the lens needs to be 5 to 10 times that of the LED element. Since the size of the LED element is about 0.5 mm × 0.5 mm, the size of the lens needs to be about 2.5 mm to 5 mm. On the other hand, in order to efficiently guide light to the light guide plate, it is necessary to increase the thickness of the light guide plate to the size of the lens. Therefore, the thickness of the light guide plate needs to be about 2.5 mm to 5 mm, which is a limitation for reducing the thickness of the liquid crystal panel.

また、CCFL及びLEDチップから放射される光は自然放出光であるため、偏光方向がランダムである。液晶パネルにおける透過率の制御は偏光を利用するため、液晶パネルは光入射側に偏光板を設置し、必要とする特定の偏光のみが液晶へ入射する構成としている。具体的には、必要とする偏光方向とは90度異なる角度の偏光の光を偏光板において吸収又は反射する。偏光板の透過率は、必要とする偏光の光ではほぼ100%であり、必要とする偏光方向とは90度異なる角度の偏光の光ではほぼ0%である。この間の偏光角度の光の透過率は、特定の偏光方向に対する角度をθとすると、cosθ×100%である。偏光方向がランダムである場合、偏光板に入射した光の約50%のみが偏光板を透過し、液晶パネルに入射する。光源装置により発生した光のうち50%を偏光板により除去して液晶表示に利用するため、光利用効率は最大でも50%となる。このように、液晶表示に利用する光エネルギーと同程度のエネルギーが有効に利用されていないという問題もある。   Moreover, since the light emitted from the CCFL and the LED chip is spontaneous emission light, the polarization direction is random. Since the transmittance of the liquid crystal panel is controlled by using polarized light, the liquid crystal panel is provided with a polarizing plate on the light incident side so that only specific polarized light that is required is incident on the liquid crystal. Specifically, light having a different angle from the required polarization direction is absorbed or reflected by the polarizing plate. The transmittance of the polarizing plate is approximately 100% for the required polarized light, and approximately 0% for the polarized light having an angle different from the required polarization direction by 90 degrees. The transmittance of light having a polarization angle during this period is cos θ × 100%, where θ is the angle with respect to a specific polarization direction. When the polarization direction is random, only about 50% of the light incident on the polarizing plate passes through the polarizing plate and enters the liquid crystal panel. Since 50% of the light generated by the light source device is removed by the polarizing plate and used for liquid crystal display, the light utilization efficiency is 50% at the maximum. As described above, there is a problem that the same energy as the light energy used for the liquid crystal display is not effectively used.

本発明は、前記の問題を解決し、光源装置に用いた場合に発光光の利用効率が高い発光素子を実現できるようにすることを目的とする。   An object of the present invention is to solve the above-described problems and to realize a light-emitting element with high utilization efficiency of emitted light when used in a light source device.

具体的に、本発明に係る発光素子は、基板の主面上に形成され、第1の波長の光を発生させる活性層を有する半導体多層膜と、半導体多層膜の上に形成され、第1の2次元周期構造を構成する複数の蛍光体層とを備え、蛍光体層は、第1の波長の光に励起されて第2の波長の光を発生させ、半導体多層膜は、第1の波長の光及び第2の波長の光が導波する光導波路を有し、光導波路の端面から放射される光は、電界の方向が主面と垂直な方向の光よりも水平な方向の光の割合が高い。   Specifically, a light emitting device according to the present invention is formed on a main surface of a substrate, and has a semiconductor multilayer film having an active layer that generates light having a first wavelength, and is formed on the semiconductor multilayer film. And a plurality of phosphor layers constituting the two-dimensional periodic structure, wherein the phosphor layers are excited by light of the first wavelength to generate light of the second wavelength, and the semiconductor multilayer film has the first The light having a wavelength waveguide and a light having a second wavelength is guided, and the light emitted from the end face of the optical waveguide is light in a direction horizontal to the direction in which the direction of the electric field is perpendicular to the main surface. The percentage of is high.

本発明の発光素子は、第1の波長の光及び第2の波長の光を光導波路に閉じ込めることができるため、垂直方向の放射角及び水平方向の放射角を小さくすることができる。従って、導光板と効率良く結合したり、小さなレンズにより効率良くコリメートしたりすることが可能となる。その結果、光の利用効率を向上させることができる。   Since the light-emitting element of the present invention can confine light having the first wavelength and light having the second wavelength in the optical waveguide, the vertical emission angle and the horizontal emission angle can be reduced. Therefore, it is possible to efficiently couple with the light guide plate or collimate efficiently with a small lens. As a result, the light use efficiency can be improved.

本発明の発光素子において、第1の2次元周期構造は、第2の波長の光のうちの電界の方向が主面と垂直な方向の光に対して、フォトニックバンドギャップを形成していてもよい。このような構成とすれば、第2の波長の光は、電界の方向が基板の主面と垂直な方向であるモードが存在しなくなる。このため、電界の方向が基板の主面と平行である自然放出光及び誘導放出光のみが光導波路の内部に生じる。その結果特定の偏波方向の光を放射する発光素子を実現できる。   In the light emitting device of the present invention, the first two-dimensional periodic structure forms a photonic band gap with respect to light having a direction of an electric field perpendicular to the main surface of light having the second wavelength. Also good. With such a configuration, the light having the second wavelength does not have a mode in which the direction of the electric field is a direction perpendicular to the main surface of the substrate. For this reason, only spontaneous emission light and stimulated emission light whose electric field direction is parallel to the main surface of the substrate are generated inside the optical waveguide. As a result, a light emitting element that emits light in a specific polarization direction can be realized.

本発明の発光素子において、複数の蛍光体層のうちの光導波路の中央部に形成された蛍光体層は、第1の2次元周期構造を構成し、複数の蛍光体層のうちの光導波路の外縁部に形成された蛍光体層は、第2の2次元周期構造を構成し、第1の2次元周期構造と第2の2次元周期構造とは、周期又は周期構造を形成する基本単位の大きさ若しくは形状が互いに異なっていてもよい。この場合において、第2の2次元周期構造は、第2の波長の光のうちの電界の方向が主面と平行な方向の光に対して、フォトニックバンドギャップを形成していてもよい。このような構成とすることにより、TE偏波である第2の波長の光をさらに効率良く光導波路に閉じ込めることが可能となる。   In the light emitting device of the present invention, the phosphor layer formed in the central portion of the optical waveguide among the plurality of phosphor layers constitutes a first two-dimensional periodic structure, and the optical waveguide among the plurality of phosphor layers. The phosphor layer formed on the outer edge portion of the first layer constitutes a second two-dimensional periodic structure, and the first two-dimensional periodic structure and the second two-dimensional periodic structure form a basic unit that forms a period or a periodic structure. May have different sizes or shapes. In this case, the second two-dimensional periodic structure may form a photonic band gap with respect to light of the second wavelength light whose electric field direction is parallel to the main surface. By adopting such a configuration, it becomes possible to more efficiently confine light having the second wavelength, which is TE-polarized light, in the optical waveguide.

本発明の発光素子は、半導体多層膜と蛍光体層との間に形成された透明電極をさらに備えていてもよい。   The light emitting device of the present invention may further include a transparent electrode formed between the semiconductor multilayer film and the phosphor layer.

本発明に係る発光素子によれば、光源装置に用いた場合に発光光の利用効率が高い発光素子を実現できる。   According to the light emitting element of the present invention, a light emitting element with high utilization efficiency of emitted light can be realized when used in a light source device.

一実施形態に係る発光素子の製造方法を工程順に示す斜視図である。It is a perspective view which shows the manufacturing method of the light emitting element which concerns on one Embodiment to process order. 蛍光体層の2次元周期構造を示す平面図である。It is a top view which shows the two-dimensional periodic structure of a fluorescent substance layer. 一実施形態に係る発光素子の動作原理を示し、(a)は端面における断面図であり、(b)は光導波路に沿った方向の断面図である。The operation principle of the light emitting element concerning one embodiment is shown, (a) is a sectional view in an end face, and (b) is a sectional view of a direction along an optical waveguide. 蛍光体層により形成されたフォトニック結晶のフォトニックバンド構造を示す図である。It is a figure which shows the photonic band structure of the photonic crystal formed of the fluorescent substance layer. (a)及び(b)は、それぞれ波長440nm及び波長570nmにおける半導体多層膜中の光分布を示す図である。(A) And (b) is a figure which shows the light distribution in the semiconductor multilayer film in wavelength 440nm and wavelength 570nm, respectively. 蛍光体層の2次元周期構造の変形例を示す平面図である。It is a top view which shows the modification of the two-dimensional periodic structure of a fluorescent substance layer. 光導波路の外縁部に形成された蛍光体層におけるフォトニックバンド構造を示す図である。It is a figure which shows the photonic band structure in the fluorescent substance layer formed in the outer edge part of an optical waveguide. 一実施形態に係る発光素子を液晶パネルのバックライトに用いた例を示す図である。It is a figure which shows the example which used the light emitting element which concerns on one Embodiment for the backlight of a liquid crystal panel. 一実施形態に係る発光素子をプロジェクタの光源に用いた例を示す図である。It is a figure which shows the example which used the light emitting element which concerns on one Embodiment for the light source of a projector.

最初に、一実施形態に係る発光素子の構成及びその製造方法について、図面を参照して説明する。まず、図1(a)に示すように、主面の面方位が(0001)面であるn型のGaNからなる基板101の上に、有機金属気相成長(MOCVD)法等により窒化物半導体からなる半導体多層膜102を形成する。半導体多層膜102は、例えば基板101側から順次形成されたn型クラッド層121、活性層122、p側光ガイド層123、電子オーバーフローストップ層(OFS層、図示せず)及びp型コンタクト層125とすればよい。n型クラッド層121は、膜厚が1.6μmでシリコン(Si)濃度が5×1017cm-3のn型Al0.8In0.2Nとすればよい。活性層122は、膜厚が3nmのIn0.25Ga0.85Nからなる井戸層と膜厚が7nmのアンドープIn0.03Ga0.97Nからなる障壁層とが積層された2重量子井戸構造とすればよい。この場合の発光波長は約440nmとなる。p側光ガイド層123は、膜厚が50nmのアンドープIn0.02Ga0.98Nとすればよい。OFS層は、膜厚が10nmでMg濃度が1×1019cm-3のp型Al0.2Ga0.8Nとすればよい。p型コンタクト層125は膜厚が50nmでMg濃度が3×1019cm-3のp型GaNとすればよい。これらの、組成及び膜厚等は一例であり適宜変更してかまわない。 First, a configuration of a light emitting device and a manufacturing method thereof according to an embodiment will be described with reference to the drawings. First, as shown in FIG. 1A, a nitride semiconductor is formed on a substrate 101 made of n-type GaN having a (0001) plane of the main surface by a metal organic chemical vapor deposition (MOCVD) method or the like. A semiconductor multilayer film 102 made of is formed. The semiconductor multilayer film 102 includes, for example, an n-type cladding layer 121, an active layer 122, a p-side light guide layer 123, an electron overflow stop layer (OFS layer, not shown), and a p-type contact layer 125, which are sequentially formed from the substrate 101 side. And it is sufficient. The n-type cladding layer 121 may be made of n-type Al 0.8 In 0.2 N having a thickness of 1.6 μm and a silicon (Si) concentration of 5 × 10 17 cm −3 . The active layer 122 may have a double quantum well structure in which a well layer made of In 0.25 Ga 0.85 N with a thickness of 3 nm and a barrier layer made of undoped In 0.03 Ga 0.97 N with a thickness of 7 nm are stacked. In this case, the emission wavelength is about 440 nm. The p-side light guide layer 123 may be undoped In 0.02 Ga 0.98 N having a thickness of 50 nm. The OFS layer may be p-type Al 0.2 Ga 0.8 N having a thickness of 10 nm and an Mg concentration of 1 × 10 19 cm −3 . The p-type contact layer 125 may be p-type GaN having a thickness of 50 nm and an Mg concentration of 3 × 10 19 cm −3 . These compositions, film thicknesses, and the like are examples and may be changed as appropriate.

次に、図1(b)に示すように、半導体多層膜102の上に、電流狭窄層103及び透明電極104を形成する。電流狭窄層103は、半導体多層膜102の上に膜厚が100nmのシリコン酸化膜(SiO2膜)を化学気相堆積(CVD)法等により堆積した後、p型コンタクト層125を露出する幅が4μm程度のストライプ状の開口部をウエットエッチング等により形成すればよい。透明電極104は、電流狭窄層103を覆い、開口部においてp型コンタクト層125と接するように膜厚が100nm程度の酸化インジウム錫(ITO)膜をスパッタ法等により形成すればよい。発光素子をスーパールミネッセンスダイオード(SLD)とする場合には、ストライプの方向をGaNからなる基板101のm軸([10−10])に対して10°程度傾けて形成すればよい。 Next, as shown in FIG. 1B, the current confinement layer 103 and the transparent electrode 104 are formed on the semiconductor multilayer film 102. The current confinement layer 103 has a width that exposes the p-type contact layer 125 after depositing a silicon oxide film (SiO 2 film) having a thickness of 100 nm on the semiconductor multilayer film 102 by a chemical vapor deposition (CVD) method or the like. May be formed by wet etching or the like. The transparent electrode 104 may be formed by sputtering or the like with an indium tin oxide (ITO) film having a thickness of about 100 nm so as to cover the current confinement layer 103 and be in contact with the p-type contact layer 125 in the opening. In the case where the light-emitting element is a super luminescence diode (SLD), the stripe direction may be inclined by about 10 ° with respect to the m-axis ([10-10]) of the substrate 101 made of GaN.

次に、図1(c)に示すように、セリウムにより賦活したイットリウムアルミニウムガーネット(YAG:Ce)からなる複数の蛍光体層105を形成する。蛍光体層105はスパッタ法等により膜厚が100nm程度の蛍光体を堆積した後、電子ビーム露光等のリソグラフィとドライエッチング等を用いて形成すればよい。各蛍光体層105は例えば、直径2rが128.5nmの円柱状とし、周期aが257nmの三角格子状に配列すればよい。また、図2に示すように、第1ブリルアンゾーンにおいてM点がストライプの方向と一致するように配列する。   Next, as shown in FIG. 1C, a plurality of phosphor layers 105 made of yttrium aluminum garnet (YAG: Ce) activated by cerium are formed. The phosphor layer 105 may be formed by depositing a phosphor having a thickness of about 100 nm by sputtering or the like and then using lithography such as electron beam exposure and dry etching. Each phosphor layer 105 may be, for example, a cylindrical shape having a diameter 2r of 128.5 nm and a triangular lattice shape having a period a of 257 nm. Further, as shown in FIG. 2, the M points are arranged in the first Brillouin zone so as to coincide with the stripe direction.

次に、図1(d)に示すように、p電極107及びn電極108を形成する。p電極107は、透明電極104の上に選択的に形成したチタン(Ti)、アルミニウム(Al)、白金(Pt)及び金(Au)の積層膜(Ti/Al/Pt/Au)とすればよい。n電極108は基板101をダイシングしやすいように薄膜化した後、基板101の裏面にTi/Al/Pt/Auを形成すればよい。   Next, as shown in FIG. 1D, a p-electrode 107 and an n-electrode 108 are formed. If the p-electrode 107 is a laminated film (Ti / Al / Pt / Au) of titanium (Ti), aluminum (Al), platinum (Pt) and gold (Au) selectively formed on the transparent electrode 104. Good. After the n-electrode 108 is thinned so that the substrate 101 can be easily diced, Ti / Al / Pt / Au may be formed on the back surface of the substrate 101.

図1(a)〜(d)では、1つの発光素子について図示したが、実際にはウェハ上に複数の発光素子を形成した後、ウェハの(10−10)面であるm面を露出する1次劈開と、(11−20)面であるa面を露出する2次劈開を行い個片化する。   Although FIGS. 1A to 1D illustrate one light emitting element, in practice, after a plurality of light emitting elements are formed on the wafer, the m-plane which is the (10-10) plane of the wafer is exposed. A primary cleavage and a secondary cleavage that exposes the a-plane which is the (11-20) plane are performed to make individual pieces.

発光素子のチップサイズは、図示していないボンディングパッド領域を含めて、チップ幅を200μmとし、チップ長を800μmとすればよい。   As for the chip size of the light emitting element, the chip width may be 200 μm and the chip length may be 800 μm including the bonding pad region (not shown).

以下に、本実施形態の発光素子の動作について、図3を用いて説明する。図3(a)はストライプと垂直な方向の断面の構成を示し、図3(b)はストライプに沿った方向の断面の構成を示している。   Hereinafter, the operation of the light emitting device of this embodiment will be described with reference to FIG. FIG. 3A shows a cross-sectional configuration in the direction perpendicular to the stripe, and FIG. 3B shows a cross-sectional configuration in the direction along the stripe.

p電極107から透明電極104、p型コンタクト層125を介して活性層122に正孔が注入され、n電極108から基板101及びn型クラッド層121を介して活性層122に電子が注入される。活性層122の電流狭窄層103が形成されていない部分のほぼ直下において正孔と電子とが再結合することにより、波長が約440nmの青色の自然放出光が発生する。ITOからなる透明電極104の屈折率は2.1であり、SiO2からなる電流狭窄層103の屈折率は1.46である。このため、屈折率が高い透明電極104が装荷層となり光導波路109が形成される。光導波路109の導波モードと結合した自然放出光は、光導波路109の内部を伝搬する。 Holes are injected from the p electrode 107 into the active layer 122 through the transparent electrode 104 and the p-type contact layer 125, and electrons are injected from the n electrode 108 into the active layer 122 through the substrate 101 and the n-type cladding layer 121. . Holes and electrons recombine almost immediately below the portion of the active layer 122 where the current confinement layer 103 is not formed, whereby blue spontaneous emission light having a wavelength of about 440 nm is generated. The refractive index of the transparent electrode 104 made of ITO is 2.1, and the refractive index of the current confinement layer 103 made of SiO 2 is 1.46. Therefore, the transparent electrode 104 having a high refractive index serves as a loading layer, and the optical waveguide 109 is formed. Spontaneous emission light combined with the waveguide mode of the optical waveguide 109 propagates inside the optical waveguide 109.

p電極107とn電極108との間に印加する電圧を増大させることにより、活性層122へ注入されるキャリア密度が上昇する。キャリア密度が透明化キャリア密度を超えると、活性層122による誘導放出が開始され、導波光が光増幅される。活性層122を量子井戸構造とすることにより、電界の方向が半導体多層膜102の積層方向、つまり基板101の主面と垂直な方向の導波光であるTM偏光よりも、電界の方向が基板101の主面と平行な方向の導波光であるTE偏光の光増幅率(光利得)が高くなる。このため、光増幅された導波光においては、TE偏光がTM偏光よりも多く存在する。具体的には、TE偏光比(TE偏光/TM偏光)は15よりも大きい。   Increasing the voltage applied between the p-electrode 107 and the n-electrode 108 increases the density of carriers injected into the active layer 122. When the carrier density exceeds the transparent carrier density, stimulated emission by the active layer 122 is started, and the guided light is amplified. By making the active layer 122 have a quantum well structure, the direction of the electric field is higher than that of the TM polarized light in which the direction of the electric field is guided in the stacking direction of the semiconductor multilayer film 102, that is, the direction perpendicular to the main surface of the substrate 101. The optical amplification factor (optical gain) of TE-polarized light, which is guided light in a direction parallel to the main surface of the, becomes high. For this reason, in the optically amplified guided light, there are more TE polarized light than TM polarized light. Specifically, the TE polarization ratio (TE polarization / TM polarization) is greater than 15.

端面反射により光増幅の正帰還が発生し、光利得が閾値を越えるとレーザ発振が生じる。本実施形態においては、光導波路を形成するストライプをm軸に対して10°傾斜させている。このため、光導波路端面に対する導波光の反射率(モード反射率)が低減され、レーザ発振を抑えている。従って、コヒーレンス性が低くスペックルノイズが小さいスーパールミネッセンスダイオードが形成されている。   Positive feedback of optical amplification occurs due to end face reflection, and laser oscillation occurs when the optical gain exceeds a threshold value. In this embodiment, the stripe forming the optical waveguide is inclined by 10 ° with respect to the m-axis. For this reason, the reflectivity (mode reflectivity) of the guided light with respect to the end face of the optical waveguide is reduced, and laser oscillation is suppressed. Therefore, a super luminescence diode having low coherence and low speckle noise is formed.

YAG:Ceからなる蛍光体層105は、光増幅されて伝搬する青色光を吸収する。CeをドープしたYAG母体が青色光を吸収することにより、励起子が発生し、発光中心であるCeにエネルギー移動する。このため、Ceに由来した波長が570nm程度の黄色光が発生する。   The phosphor layer 105 made of YAG: Ce absorbs blue light that is amplified and propagated. When the YAG matrix doped with Ce absorbs blue light, excitons are generated and energy is transferred to Ce, which is the emission center. For this reason, yellow light having a wavelength derived from Ce of about 570 nm is generated.

蛍光体層105は2次元周期構造を有しており、励起子の発光において2次元フォトニック結晶として機能する。図4は、2次元フォトニック結晶中における真空中の波長がλの光に対するフォトニックバンド構造を平面展開法により理論計算した結果を示している。ωは光の振動数、cは真空中の光速度である。計算において、蛍光体層105の屈折率は2.0とし、蛍光体層105の半径rを周期aで割った値r/aは0.25とし、蛍光体層105同士の間は屈折率が1の空気により満たされているとした。図4において横軸は図2のΓ点からM点、K点を通って再びΓ点に戻る線上の位置である。   The phosphor layer 105 has a two-dimensional periodic structure and functions as a two-dimensional photonic crystal in the emission of excitons. FIG. 4 shows a result of theoretical calculation of a photonic band structure for light having a wavelength of λ in a vacuum in a two-dimensional photonic crystal by a plane expansion method. ω is the frequency of light, and c is the speed of light in a vacuum. In the calculation, the refractive index of the phosphor layer 105 is 2.0, the value r / a obtained by dividing the radius r of the phosphor layer 105 by the period a is 0.25, and the refractive index is between the phosphor layers 105. 1 was filled with air. In FIG. 4, the horizontal axis is the position on the line from the Γ point in FIG. 2 through the M point and the K point to the Γ point again.

図4に示すように、a/λが0.4〜0.5程度の範囲にTM偏光に対するフォトニックバンドギャップが存在する。このため、aが257nmの場合には、λが514nm〜642nmの範囲において、TM偏光を有する光は励起子から発生しない。従って、蛍光体層105はTE偏光の黄色光のみを蛍光として放出する。   As shown in FIG. 4, a photonic band gap for TM polarized light exists in the range where a / λ is about 0.4 to 0.5. For this reason, when a is 257 nm, light having TM polarization is not generated from excitons in the range of λ from 514 nm to 642 nm. Therefore, the phosphor layer 105 emits only TE-polarized yellow light as fluorescence.

以上説明したように、本実施形態の発光素子は、TE偏向比が高い青色光と黄色光とを発生させるため、TE偏向比が高い白色光源として機能する。   As described above, the light emitting element of the present embodiment generates blue light and yellow light having a high TE deflection ratio, and thus functions as a white light source having a high TE deflection ratio.

また、本実施形態の発光素子は、光導波路が黄色光に対しても光導波機能を有している。図5(a)及び(b)は、それぞれ伝達マトリクス法により半導体多層膜102の積層方向における光分布を波長440nmの光及び波長570nmの光について計算した結果を示している。蛍光体層105は、r/aが0.25の円柱が配列された層である。このため、計算においては、実効的な体積充填率が55.5%であり、平均的な屈折率が1.56の均一層として近似した。本実施形態の発光素子は、GaNと格子整合するが、屈折率が2.2でありGaNとの屈折率が0.3であるAl0.8In0.2Nをn型クラッド層121としている。このため、図5に示すように、波長440nm及び波長570nmのいずれにおいても、半導体多層膜102の積層方向に対して光を強く閉じ込めることが可能である。なお、図5に示す積層方向の光分布に基づいて、光導波路端面からの放射角度を計算すると、垂直方向の遠視野分布の半値全幅θvは波長が440nmの場合には約54°となり、波長570nmの場合には約50°となった。この値は、通常のLEDと比べると十分に狭放射であることを示している。 In the light emitting device of this embodiment, the optical waveguide has an optical waveguide function even for yellow light. FIGS. 5A and 5B show the results of calculating the light distribution in the stacking direction of the semiconductor multilayer film 102 for the light with a wavelength of 440 nm and the light with a wavelength of 570 nm by the transfer matrix method, respectively. The phosphor layer 105 is a layer in which cylinders having r / a of 0.25 are arranged. For this reason, in the calculation, an effective volume filling factor was 55.5%, and an approximation was made as a uniform layer having an average refractive index of 1.56. In the light emitting device of this embodiment, Al 0.8 In 0.2 N having lattice matching with GaN but having a refractive index of 2.2 and a refractive index of GaN of 0.3 is used as the n-type cladding layer 121. For this reason, as shown in FIG. 5, it is possible to confine light strongly with respect to the stacking direction of the semiconductor multilayer film 102 at both of the wavelength 440 nm and the wavelength 570 nm. When the radiation angle from the end face of the optical waveguide is calculated based on the light distribution in the stacking direction shown in FIG. 5, the full width at half maximum θv of the far field distribution in the vertical direction is about 54 ° when the wavelength is 440 nm. In the case of 570 nm, it was about 50 °. This value indicates that the radiation is sufficiently narrow compared with a normal LED.

また、水平方向の屈折率差Δnを等価屈折率法により計算すると、波長440nmの場合には5.06×10-3となり、波長570nmの場合には1.10×10-2となった。光導波路の幅を4μmとして、得られたΔnの値に基づいて水平方向の遠視野分布の半値全幅θhを計算すると、波長440nmの場合には約6°となり、波長570nmの場合には約7°となった。この値は、通常のLEDと比べると非常に狭放射であることを示している。 Further, when the refractive index difference Δn in the horizontal direction was calculated by the equivalent refractive index method, it was 5.06 × 10 −3 at the wavelength of 440 nm and 1.10 × 10 −2 at the wavelength of 570 nm. When the width of the optical waveguide is 4 μm and the full width at half maximum θh of the far-field distribution in the horizontal direction is calculated based on the obtained Δn value, it is about 6 ° for the wavelength 440 nm and about 7 for the wavelength 570 nm. It became °. This value indicates that the emission is very narrow compared to a normal LED.

本実施形態においては、蛍光体層105を光導波路となる領域の上に一定の2次元(屈折率)周期構造となるように配列した。しかし、図6に示すように光導波路の中央部109aの上に形成した蛍光体層105aと外縁部109bの上に形成した蛍光体層105bとが異なる周期構造となるように配置してもよい。図6においては、導波路の中央部109aである幅が約2.8μmの領域においては、蛍光体層105aを直径2rが128.5nmで、周期aが257nmの三角格子状に配置している。一方、光導波路の外縁部109bである幅が約0.8μmの領域においては、直径が210.7nmの開口部105cを周期aが257nmの三角格子状に形成した蛍光体層105bを形成している。なお、いずれの三角格子においても、第1ブリルアンゾーンにおいてM点がストライプの方向と一致するように配列している。   In the present embodiment, the phosphor layer 105 is arranged on the region serving as the optical waveguide so as to have a constant two-dimensional (refractive index) periodic structure. However, as shown in FIG. 6, the phosphor layer 105a formed on the central portion 109a of the optical waveguide and the phosphor layer 105b formed on the outer edge portion 109b may be arranged to have different periodic structures. . In FIG. 6, the phosphor layer 105a is arranged in a triangular lattice shape having a diameter 2r of 128.5 nm and a period a of 257 nm in the central portion 109a of the waveguide having a width of about 2.8 μm. . On the other hand, in the region having a width of about 0.8 μm, which is the outer edge portion 109b of the optical waveguide, a phosphor layer 105b in which openings 105c having a diameter of 210.7 nm are formed in a triangular lattice shape having a period a of 257 nm is formed. Yes. In any triangular lattice, the M points are arranged in the first Brillouin zone so as to coincide with the stripe direction.

図7は、外縁部109bにおけるフォトニックバンド構造を計算により求めた結果を示している。図7に示すように、外縁部109bにおいては、a/λが0.4〜0.5程度の範囲にTE偏光に対するフォトニックバンドギャップが存在する。このため、aが257nmの場合には、λが514nm〜642nmの範囲において、TE偏光の導波光は、光導波路の外縁部109bにどの様な角度により入射しても全反射される。従って、蛍光体層105から放出されたTE偏光の黄色光は、光導波路109の内部に閉じ込められ、光導波路109の側方にほとんど漏れ出さない。その結果、黄色光に対する発光効率をより向上させることが可能となる。   FIG. 7 shows the result of calculating the photonic band structure at the outer edge 109b by calculation. As shown in FIG. 7, in the outer edge portion 109b, a photonic band gap for TE polarized light exists in a range where a / λ is about 0.4 to 0.5. For this reason, when a is 257 nm, TE-polarized guided light is totally reflected at any angle on the outer edge 109 b of the optical waveguide in the range of λ from 514 nm to 642 nm. Therefore, the TE-polarized yellow light emitted from the phosphor layer 105 is confined inside the optical waveguide 109 and hardly leaks to the side of the optical waveguide 109. As a result, the luminous efficiency for yellow light can be further improved.

中央部109aに形成した蛍光体層105aと、外縁部109bに形成した蛍光体層105bとを互いに異なった形状とすることにより、中央部109aと外縁部109bとに異なる2次元周期構造を形成する例を示した。しかし、2次元周期構造を形成する基本単位である蛍光体層105aの周期aと、蛍光体層105bの周期aとが互いに異なっている構成としてもよく、周期を構成する基本単位である蛍光体層105aの半径rと蛍光体層105bの半径rとが互いに異なっている構成としてもよい。また、周期aと半径rとの両方が互いに異なっている構成であってもよい。   The phosphor layer 105a formed at the central portion 109a and the phosphor layer 105b formed at the outer edge portion 109b have different shapes, thereby forming different two-dimensional periodic structures at the central portion 109a and the outer edge portion 109b. An example is shown. However, the period a of the phosphor layer 105a, which is a basic unit forming a two-dimensional periodic structure, and the period a of the phosphor layer 105b may be different from each other, and the phosphor that is a basic unit constituting the period. The radius r of the layer 105a and the radius r of the phosphor layer 105b may be different from each other. Moreover, the structure from which both the period a and the radius r mutually differ may be sufficient.

また、本実施形態ではフォトニックバンドギャップが形成されやすい三角格子を用いて発明を説明したが、2次元周期構造は三角格子に限らず、所定のフォトニックバンドギャップが形成できればどの様な周期構造であってもよい。具体的には、正方格子や斜方格子等であってもよい。   In the present embodiment, the invention has been described using a triangular lattice in which a photonic band gap is easily formed. However, the two-dimensional periodic structure is not limited to a triangular lattice, and any periodic structure can be formed as long as a predetermined photonic band gap can be formed. It may be. Specifically, a square lattice, an oblique lattice, or the like may be used.

図8は、本実施形態の発光素子200を液晶パネル210のバックライトに用いた例を示している。発光素子200から出射された光は、導光板201の内部を進行し、所定の方向に出射され、全反射プリズム202に入射する。全反射プリズム202により液晶パネルと垂直な方向に屈折された光は入射側の偏光板211、液晶パネル210及び出射側の偏光板212を通過する。   FIG. 8 shows an example in which the light emitting device 200 of the present embodiment is used for the backlight of the liquid crystal panel 210. The light emitted from the light emitting element 200 travels inside the light guide plate 201, is emitted in a predetermined direction, and enters the total reflection prism 202. The light refracted in the direction perpendicular to the liquid crystal panel by the total reflection prism 202 passes through the polarizing plate 211 on the incident side, the liquid crystal panel 210 and the polarizing plate 212 on the outgoing side.

従来のLEDは、放射角の半値全幅は120°程度であるため、LEDと導光板との結合効率が低い。一方、本実施形態の発光素子はθhが約6°〜7°と非常に狭く、θvが約50°〜54°である。このため、発光素子200の水平方向を導光板201の垂直方向と一致させ、発光素子200の垂直方向を導光板の水平方向と一致させるように配置すれば、発光素子200と導光板201との結合効率を高くすることができる。また、導光板201の面内の広い範囲へ光を拡散させることが可能となる。   Since the conventional LED has a full width at half maximum of the radiation angle of about 120 °, the coupling efficiency between the LED and the light guide plate is low. On the other hand, the light-emitting element of this embodiment has a very narrow θh of about 6 ° to 7 ° and a θv of about 50 ° to 54 °. Therefore, if the horizontal direction of the light emitting element 200 is aligned with the vertical direction of the light guide plate 201 and the vertical direction of the light emitting element 200 is aligned with the horizontal direction of the light guide plate, the light emitting element 200 and the light guide plate 201 The coupling efficiency can be increased. In addition, light can be diffused over a wide range within the surface of the light guide plate 201.

また、LEDの場合には、発生した白色光の約50%が液晶パネルの入射側に設けられた偏光板により除去されてしまう。しかし、本実施形態の発光素子200はTE偏光比が高いため、偏光板を透過する偏光方向を発光素子200のTE偏光方向と揃えておけば、偏光板211により除去される成分が少なく、光利用効率を高くすることができる。   In the case of an LED, about 50% of the generated white light is removed by the polarizing plate provided on the incident side of the liquid crystal panel. However, since the light-emitting element 200 of the present embodiment has a high TE polarization ratio, if the polarization direction transmitted through the polarizing plate is aligned with the TE polarization direction of the light-emitting element 200, less components are removed by the polarizing plate 211, and light is emitted. Utilization efficiency can be increased.

図9は、本実施形態の発光素子300をプロジェクタの光源として用いた例を示している。発光素子300から出射された光は、コリメートレンズ301により平行光とされた後、入射側の偏光板311、液晶パネル310及び出射側の偏光板312を透過する。透過した光は、光学系315により拡大されてスクリーン316に投射される。   FIG. 9 shows an example in which the light emitting element 300 of this embodiment is used as a light source of a projector. The light emitted from the light-emitting element 300 is converted into parallel light by the collimator lens 301 and then passes through the incident-side polarizing plate 311, the liquid crystal panel 310, and the outgoing-side polarizing plate 312. The transmitted light is magnified by the optical system 315 and projected onto the screen 316.

従来のLEDは、放射角の半値全幅が120°程度と大きく、光放射面積も大きい。このため、コリメートレンズに大型のレンズを用いる必要がある。しかし、本実施形態の発光素子は、放射角が最大でも50°〜54°程度であり、光放射面積も小さい。このため、コリメートレンズ301を小型にしても、効率良く光をコリメートできる。また、LEDの場合には、発生した白色光の約50%が液晶パネルの入射側に設けられた偏光板により除去されてしまう。しかし、本実施形態の発光素子300はTE偏向比が高いため、偏光板311により除去される成分が少なく、光利用効率を高くすることができる。   The conventional LED has a large full width at half maximum of the radiation angle of about 120 ° and a large light radiation area. For this reason, it is necessary to use a large lens for the collimating lens. However, the light emitting element of this embodiment has a maximum radiation angle of about 50 ° to 54 ° and a small light emission area. For this reason, even if the collimating lens 301 is made small, light can be collimated efficiently. In the case of an LED, about 50% of the generated white light is removed by the polarizing plate provided on the incident side of the liquid crystal panel. However, since the light emitting element 300 of the present embodiment has a high TE deflection ratio, there are few components removed by the polarizing plate 311 and the light utilization efficiency can be increased.

なお、本実施形態において、GaN系の半導体多層膜からなる青色のSLDと、YAG:Ceからなる黄色の蛍光体とを用いた白色発光素子について説明した。しかし、これに限らずその他の形態や材料であってもよい。例えば、GaN系の半導体多層膜からなる青色のレーザダイオードと緑色及び赤色の蛍光体との組み合わせとしたり、GaN系の半導体多層膜からなる紫外SLDと青色、緑色及び赤色の蛍光体との組み合わせとしたりして白色の発光素子を形成する場合にも同様の手法を用いることができる。   In the present embodiment, a white light emitting element using a blue SLD made of a GaN-based semiconductor multilayer film and a yellow phosphor made of YAG: Ce has been described. However, it is not limited to this, and other forms and materials may be used. For example, a combination of a blue laser diode made of a GaN-based semiconductor multilayer film and a green and red phosphor, or a combination of an ultraviolet SLD made of a GaN-based semiconductor multilayer film and a blue, green, and red phosphor. The same technique can be used when forming a white light emitting element.

また、白色の発光素子に限らず、導波路型発光素子と蛍光体とを集積した発光素子において、蛍光体からの発光の偏光方向を制御する目的にも適用できる。従って、半導体多層膜はGaN系に限らず、AlInGaP系又はAlGaAs系等の半導体多層膜を用いた赤色又は赤外の発光素子と、蛍光体とを組み合わせる場合にも適用することができる。さらに、蛍光体はYAG:Ceのように酸化物に希土類元素をドープした材料だけでなく、有機色素、ZnS若しくはCdSe等からなる半導体ナノ粒子を分散させたポリマー又は酸化物ガラス等であってもよい。   Further, the present invention is not limited to a white light emitting element, and can be applied to the purpose of controlling the polarization direction of light emitted from a phosphor in a light emitting element in which a waveguide type light emitting element and a phosphor are integrated. Therefore, the semiconductor multilayer film is not limited to the GaN system, but can be applied to a combination of a phosphor with a red or infrared light emitting element using a semiconductor multilayer film such as an AlInGaP system or an AlGaAs system. Further, the phosphor may be not only a material in which an oxide is doped with a rare earth element, such as YAG: Ce, but also a polymer or oxide glass in which semiconductor nanoparticles made of an organic dye, ZnS, CdSe, or the like are dispersed. Good.

本発明に係る発光素子は、光源装置に用いた場合に発光光の利用効率が高く、特にバックライト及びプロジェクタ等の光源として有用である。   The light emitting element according to the present invention has high utilization efficiency of emitted light when used in a light source device, and is particularly useful as a light source for backlights, projectors and the like.

101 基板
102 半導体多層膜
103 電流狭窄層
104 透明電極
105 蛍光体層
105a 蛍光体層
105b 蛍光体層
105c 開口部
107 p電極
108 n電極
109 光導波路
109a 中央部
109b 外縁部
121 n型クラッド層
122 活性層
123 p側光ガイド層
125 p型コンタクト層
200 発光素子
201 導光板
202 全反射プリズム
210 液晶パネル
211 偏光板
212 偏光板
300 発光素子
301 コリメートレンズ
310 液晶パネル
311 偏光板
312 偏光板
315 光学系
316 スクリーン
DESCRIPTION OF SYMBOLS 101 Substrate 102 Semiconductor multilayer film 103 Current confinement layer 104 Transparent electrode 105 Phosphor layer 105a Phosphor layer 105b Phosphor layer 105c Opening 107 p electrode 108 n electrode 109 Optical waveguide 109a Central portion 109b Outer edge 121 n-type cladding layer 122 Active Layer 123 p-side light guide layer 125 p-type contact layer 200 light emitting element 201 light guide plate 202 total reflection prism 210 liquid crystal panel 211 polarizing plate 212 polarizing plate 300 light emitting element 301 collimating lens 310 liquid crystal panel 311 polarizing plate 312 polarizing plate 315 optical system 316 screen

Claims (5)

基板の主面上に形成され、第1の波長の光を発生させる活性層を有する半導体多層膜と、
前記半導体多層膜の上に形成され、第1の2次元周期構造を構成する複数の蛍光体層とを備え、
前記蛍光体層は、前記第1の波長の光に励起されて第2の波長の光を発生させ、
前記半導体多層膜は、前記第1の波長の光及び第2の波長の光が導波する光導波路を有し、
前記光導波路の端面から放射される前記第1の波長の光及び第2の波長の光は、電界の方向が前記主面と垂直な方向の光よりも水平な方向の光の割合が高いことを特徴とする発光素子。
A semiconductor multilayer film having an active layer formed on the main surface of the substrate and generating light of a first wavelength;
A plurality of phosphor layers formed on the semiconductor multilayer film and constituting a first two-dimensional periodic structure;
The phosphor layer is excited by the light of the first wavelength to generate light of the second wavelength,
The semiconductor multilayer film has an optical waveguide through which the light of the first wavelength and the light of the second wavelength are guided,
The first wavelength light and the second wavelength light emitted from the end face of the optical waveguide have a higher proportion of light in a horizontal direction than light in a direction perpendicular to the main surface of the electric field. A light emitting device characterized by the above.
前記第1の2次元周期構造は、前記第2の波長の光のうちの電界の方向が前記主面と垂直な方向の光に対して、フォトニックバンドギャップを形成していることを特徴とする請求項1に記載の発光素子。   The first two-dimensional periodic structure is characterized in that a photonic band gap is formed with respect to light whose direction of electric field is perpendicular to the main surface of the light having the second wavelength. The light emitting device according to claim 1. 前記複数の蛍光体層のうちの前記光導波路の中央部に形成された蛍光体層は、前記第1の2次元周期構造を構成し、
前記複数の蛍光体層のうちの前記光導波路の外縁部に形成された蛍光体層は、第2の2次元周期構造を構成し、
前記第1の2次元周期構造と前記第2の2次元周期構造とは、周期又は周期構造を形成する基本単位の大きさ若しくは形状が互いに異なっていることを特徴とする請求項1又は2に記載の発光素子。
A phosphor layer formed in a central portion of the optical waveguide among the plurality of phosphor layers constitutes the first two-dimensional periodic structure,
The phosphor layer formed on the outer edge of the optical waveguide among the plurality of phosphor layers constitutes a second two-dimensional periodic structure,
3. The first two-dimensional periodic structure and the second two-dimensional periodic structure are different from each other in size or shape of a basic unit forming the period or the periodic structure. The light emitting element of description.
前記第2の2次元周期構造は、前記第2の波長の光のうちの電界の方向が前記主面と平行な方向の光に対して、フォトニックバンドギャップを形成していることを特徴とする請求項3に記載の発光素子。   The second two-dimensional periodic structure is characterized in that a photonic band gap is formed with respect to light whose direction of electric field is parallel to the main surface of the light having the second wavelength. The light emitting device according to claim 3. 前記半導体多層膜と前記蛍光体層との間に形成された透明電極をさらに備えていることを特徴とする請求項1〜4のいずれか1項に記載の発光素子。   The light emitting device according to claim 1, further comprising a transparent electrode formed between the semiconductor multilayer film and the phosphor layer.
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